1. Technical Field
This invention relates to a new stabilized form of gas-enriched liquid produced by a process comprising generally the steps of: preparing a mixture of a gas and a liquid; compressing the mixture so that the gas completely dissolves in the liquid to form a gas-enriched liquid either before or after enclosing the mixture in a confined space.
2. Description of Background Art
The maximum concentration of gas achievable in a liquid ordinarily is governed by Henry""s Law. At ambient pressure, the relatively low solubility of many gases, such as oxygen or nitrogen, within a liquid such as water produces a low concentration of the gas in the liquid. However, there are many applications wherein it would be advantageous to employ a gas concentration within the liquid which greatly exceeds its solubility at ambient pressure. Compression of a gas/liquid mixture at a high pressure can be used to achieve a high dissolved gas concentration, but disturbance of a gas-supersaturated liquid by attempts to eject it into a 1 bar environment from a high pressure reservoir ordinarily results in cavitation inception at or near the exit port. The rapid evolution of bubbles produced at the exit port vents much of the gas from the liquid, so that a high degree of gas-supersaturation no longer exists in the liquid at ambient pressure outside the high pressure vessel. In addition, the presence of bubbles in the effluent generates turbulence and impedes the flow of the effluent beyond the exit port.
U.S. Pat. No. 4,664,680 relates to enriching the oxygen content of water. That reference discloses a number of conventional types of apparatus that can be used for continuously contacting liquid and oxygen-containing gas streams to effect oxygen absorption. To avoid premature liberation of dissolved oxygen before it is incorporated within the bulk of matter to be enriched in oxygen content, pressurizable confined flow passageways are used.
Other oxygen saturation devices are disclosed in U.S. Pat. Nos. 4,874,509; and 4,973,558. These and other approaches leave unsolved the need to infuse gas enriched fluid solutions from a high pressure reservoir toward a reaction site at a lower pressure without cavitation or bubble formation in the effluent at or near the exit port.
In a co-pending application Ser. No. 152,589, filed Nov. 15, 1993 now U.S. Pat. No. 5,407,426, a method is described for the stabilization of a stream of oxygen-supersaturated water which permitted ejection of the stream from a high pressure vessel into a 1 bar environment without cavitation inception in the effluent at or near the exit port(s). An effluent of water containing oxygen at a concentration as high as on the order of 4 cc oxygen/g of injectate, representing a partial pressure of approximately 140 bar of the dissolved gas, can be ejected from a high pressure vessel into a 1 bar liquid environment with complete absence of cavitation inception in the ejected stream. In air at 1 bar, cavitation inception in a high velocity stream is delayed until breakup of the ejected stream into droplets.
The absence of cavitation inception in water supersaturated with oxygen at a high concentration permits its in vivo infusion into either venous or arterial blood for the purpose of increasing the oxygen concentration of blood without incurring the formation of bubbles which would otherwise occlude capillaries.
In addition to this application as previously described, a wide variety of other applications would benefit from ejection of a gas-supersaturated fluid from a high pressure reservoir into an ambient pressure environment in a manner which is unassociated with cavitation inception at or near the exit port. For example, organic material and plant waste streams, e.g., paper mills and chemical plants, often require an increase in dissolved oxygen content before the discharge of such waste streams in a body of water. U.S. Pat. No. 5 4,965,022 also recognizes that a similar need may also occur at municipal waste treatment plants and that fish farms require increased dissolved oxygen levels to satisfy the needs of high density aquaculture. Other applications are disclosed in my U.S. Pat. No. 5,261,875.
A method is described for ejection of gas-supersaturated fluids or liquids from a high pressure reservoir to a relatively low pressure environment, including ambient pressure, which permits the use of the gas-supersaturated liquid at the lower pressure without immediate cavitation inception. Cavitation nuclei in the liquid are removed by compression in a high pressure reservoir. The use of suitable channels at the distal end of the system for delivery of the gas-supersaturated liquid, plus elimination of cavitation nuclei along the inner surface of the channels, allow ejection of the liquid into a relatively low pressure environment without cavitation inception at or near the exit port.
Thus, an important aspect of the invention described herein is the use of capillary channels at the distal end of the delivery system, along with initial hydrostatic compression of a liquid to remove cavitation nuclei along the inner surface of the channels. When such nuclei contain a relatively insoluble gas, such as oxygen or nitrogen, a hydrostatic pressure of 0.5 to 1.0 kbar is highly effective for this purpose. For nuclei of a soluble gas, such as carbon dioxide, a lower hydrostatic pressure can be used for their dissolution. Cavitation nuclei and bubbles in the bulk liquid are removed in the high pressure reservoir by either direct hydrostatic compression, for example, from movement of a liquid or piston driven by a hydraulic compressor, or by compression from a source of gas maintained at a pressure which would provide the desired concentration of gas in the liquid. Hydrostatic compression to 0.1 to 1.0 kbar rapidly removes cavitation nuclei and bubbles from the liquid, but much lower pressures from a gas source are also effective, although requiring longer periods of time. When a gas source is used to both pressurize the liquid and achieve a desired concentration of a relatively insoluble gas in the liquid, the range of gas pressure would typically be in the 10 bar to 150 bar range. When a highly soluble gas, such as carbon dioxide is used, a lower gas pressure, in the range of 2 to 8 bar would typically be employed to achieve a dissolved gas concentration of interest, and a higher level of hydrostatic pressure, on the order of 0.1 kbar to 1.0 kbar, is then applied to remove gas nuclei.
As a result of the lack of cavitation inception at or near the exit port, a stream of gas-supersaturated liquid can be used to enrich a gas-deprived liquid with gas outside the high pressure reservoir simply by convection of the gas-supersaturated effluent with the gas-deprived liquid at ambient pressure. Enrichment of a gas-deprived liquid with gas by diffusion from the gas phase to the liquid is, by contrast, an extremely slow process. The lack of bubbles in the effluent additionally permits unimpeded ejection into the gas-deprived liquid. When the gas-supersaturated liquid is ejected in an air environment, the lack of cavitation inception at or near the exit port facilitates the use of the effluent in a manner similar to use of the same liquid which is not supersaturated with gas, i.e., the ejected stream remains intact, rather than becoming disintegrated into a diffuse spray near the exit port from rapid growth of gas nuclei.
Based on the teachings in the above applications and U.S. patents and the disclosure in the present application that more particularly point to certain embodiments of these teachings, the presently claimed invention provides a stabilized gas-enriched liquid produced by a process comprising the steps of:
a) preparing a mixture of gas and liquid;
b) compressing the mixture to a pressure such that the gas completely dissolves in the liquid to form a gas-enriched liquid;
c) enclosing the gas-enriched liquid within a confined space while retaining substantially the same pressure,
wherein the confined space has at least one dimension less than about 0.2 mm, preferably in the range of about 0.01 micron to about 200 micron.
Alternatively, a stabilized gas-supersaturated liquid can be produced by a process comprising the steps of:
a) preparing a mixture of gas and liquid;
b) enclosing the mixture within a confined space;
c) compressing the mixture within the confined space to a pressure such that the gas completely dissolves in the liquid to form a gas-enriched liquid.
The presently claimed invention additionally provides a stabilized gas-supersaturated liquid produced by a process of steps a), b), and c), as above with the further step of d) lowering the hydrostatic pressure to a value below the dissolved gas partial pressure, within at least some portion of the space, without bubble nucleation.
The gas used in the mixture may be oxygen, nitrogen, argon, helium, carbon dioxide, ozone, and mixtures thereof. Virtually any gas may be used, as described in the above cited co-pending U.S. patent applications. As an additional example, carbon monoxide, which has a solubility in water similar to that of oxygen, could be used for the purpose of enhancing the industrial production of organic compounds by anaerobic bacteria. The liquid used in the mixture may be water, an alcohol, a ketone, an oil, a hydrocarbon, and mixtures thereof. The liquid may contain dissolved salts. A particularly preferred gas-enriched liquid is where the gas is oxygen and the liquid is an aqueous solution, such as water, saline solution or a physiological fluid. Preferably, the concentration of oxygen is in the range of 0.06 ml O2 (STP)/g to 4.0 ml O2 (STP)/g.
A preferred manner of enclosing the gas-enriched liquid within a confined space while retaining substantially the same pressure in the process described above is to deliver the gas-enriched liquid to a capillary tube having a hydrophilic surface and an internal diameter that retains the gas in solution and prevents formation of bubbles in the gas-enriched liquid. Alternatively, before the mixture of gas and liquid is compressed, it is delivered into such a capillary tube and then compressed such that the gas completely dissolves in the liquid to form a gas-enriched liquid within the capillary tube. The capillary tube preferably comprises glass, quartz, silica or metal. It is particularly preferred that the capillary tube be a tubing having an internal diameter of 2 to 200 microns. Another embodiment of the process for producing the gas-supersaturated liquid is to enclose the gas-enriched liquid within a porous matrix containing a plurality of capillary spaces. Such a matrix may be selected from the group consisting of porous ceramics, porous polymers, porous metals and hydrogels. The minimum spatial dimension of such spaces can range from 0.01 micron to 200 microns.
One benefit of the present invention is that a gas-supersaturated liquid produced is stable for sufficiently useful periods of time when the gas-enriched liquid is injected into a liquid environment of interest having a low concentration of the gas if the rate of flow permits mixing of the gas-enriched liquid with the environment before bubble nucleation can occur. The preferred liquid environment of interest comprises blood, water, hazardous waste material, liquid glass, a polymer, or a liquid metal. A particularly preferred embodiment is where the gas is oxygen and the liquid environment of interest is blood.
An alternative embodiment of the present invention provides a gas-supersaturated liquid produced by the process comprising the steps of:
a) preparing a mixture of gas hydrate particles and a liquid;
b) compressing the mixture so that the particles at least partially dissolve in the liquid to form a gas-enriched liquid; and
c) delivering the gas-enriched liquid while retaining substantially the same pressure to a capillary tube having an internal diameter that retains the gas in solution and prevents formation of bubbles in the gas-enriched liquid. The gas-enriched liquid may be injected into an environment of interest having a low concentration of the gas at a rate which permits mixing of the hydrate with the environment before bubble coalescence can occur.
As described in U.S. Pat. No. 5,261,875, another preferred embodiment of the present invention provides a gas-supersaturated liquid produced by the process comprising the steps of:
a) preparing a powdered gas hydrate;
b) mixing the hydrate with powdered ice which has a low concentration of the dissolved gas;
c) pulverizing the mixture of the hydrate and the ice into small particles;
d) encapsulating the mixture of the hydrate and the ice within a pressure vessel;
e) applying pressure to the mixture;
f) warming the pressure vessel and its contents to provide an aqueous suspension of the hydrate within the liquid water formed from the ice upon warming;
g) providing a conduit in communication with the pressure vessel and a catheter having one or more high resistance exit ports so that sufficient pressure is maintained for continued stabilization of the hydrate prior to emerging from the catheter; and
h) injecting the suspension of the particles into a liquid environment of interest at a rate which permits mixing of the hydrate with the environment before decomposition of the gas hydrate or bubble coalescence can occur to thereby form the gas-supersaturated liquid. The gas hydrate may be selected from the group consisting of oxygen hydrate, oxygen clathrate hydrate, and inert gas hydrate. The liquid environment of interest may be hypoxemic blood, hazardous waste material, liquid glass, a polymer, or a liquid metal.
One of the characteristic physical properties of the high-tensile strength form of water produced by a process comprising the steps of:
a) preparing gas-free water;
b) compressing the gas-free water to at least 100 bar; and
c) enclosing the gas-free water within a confined space while retaining the same pressure to form the high-tensile strength form of water is that the water has a boiling point of at least above 150xc2x0 C. as determined by the absence of boiling upon immersion of a loop of silica tubing 144 xcexcm o.d., 25 xcexcm i.d., containing the high tensile strength water, in a bath of silicone oil maintained at above 150xc2x0 C., for at least 40 seconds.
A characteristic physical property of an oxygen-supersaturated form of water is the absence of bubble formation when such water contains oxygen at a partial pressure of at least 50 bar in a silica tubing having an internal diameter of 20 micron or less, and is then delivered with a minimum velocity of 2 m/sec at the distal end of said tubing into at 1 bar.